An isoreactive dyeing system is a system in which the sorp tion m e is kept constant throughout the whole kinetic period. A theoretical study of this condition was carried out using the modified kinetic equation o f Cegama-Fiiente and the Arrhenius equation. The isoreactivity equation is used to determine the conditions of temperature-time which should be applied during dyeing to achieve constant sorption at different sorption times. Finally, the theoretical values and those found experimentally in the dyeing systems: wool-acid dyes, viscose rayon-direct dyes and acrylic fibres-cationic dyes are compared.
343theory is further substantiated by the work of Vail et al. l12 J who show that dimethylolacetamide finishes are not very stable to strong acid hydrolysis. This is.attributed to the electmn-donating characteristic of the methyl group.Schwenker and Pacsu [ 10 J reported that cotton could be made flame resistant by first preparing tnesyl or tosyl cellulose and then replacing the tosyl or mesyl groups with halogens. Bromine and iodine were very effective in producing flame resistance. The methylol derivative of DBCA seemed to offer an attractive and simple way of adding bromine to cotton hecause of its water solubility, and hecause conventional padding and curing techniques could he employed. Unfortunately, however, the sensitivity of the finish to relatively low temperatures removes it from the realm of a practical finish for cotton apparel goods. Fabrics with these properties may find favor in other end uses than for apparel. This work does support the theory discussed bey Schwenkcrand Pacsu r 101. The theory stages that the chemical modification of cellulose reduces the levoglucosan forming potential of cellulose and that bromine or iodine acts chemically on the flaming gases to impart flame resistance. The low decomposition point of the DHCA-treated cotton probably is a contributing factor to flame resistance.
The diffusion equation of Crank for a finite dyebath is not adequate to apply either to dyeing with high exhaustion or to annulary dyeing. It is for this reason that a systematic study of the existent empirical kinetic equations has been made. The authors also propose other new equations, based on the equation of Cegarra-Puente, which can be used to replace Crank's equation.
A dyeing method consisting of discrete additions of dye to the dyeing solution, rather than the usual practice of adding it all at the beginning, has been studied in order to assess, through a theoretical model, the precise additions required to get the same dye absorption in each constant interval of time, as well as the amount of dye to be absorbed by the fiber at each temperature so as to reach a certain level of exhaustion.
Following on from previous papers by the authors concerning the integration dyeing method, this paper studies the kinetic behaviour of the dye when integrated continuously in an isothermal solution over a period of 60 min. The dyeing systems selected were acid dyes on wool and cationic dyes on Leacril 16 fibre. Curves of the kinetics of dye absorption by the fibres were similar to those of the addition of dye to the dyebath. At low exhaustion the systems followed an Arrhenius law, contrary to the behaviour at high exhaustion where the dye absorption was almost independent from temperature. A mathematical method is described to assess the total amount of the dye to be added in relation with the desired temperature and exhaustion.
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